Speciation of Fe(II) and Fe(III) by the modified ferrozine method,FIA-spectrophotometry,and flame AAS after cloud-point extraction

A method has been developed for the simultaneous determination of traces of Fe(III) and Fe(II) in water by on-line coupling of spectrophotometry with flame atomic absorption spectrometry (FAAS). The method involves cloud-point extraction (CPE) of both species with ammonium pyrrolidinecarbodithioate (APDC) under standard conditions, which facilitates the in situ complexation and extraction of both species. Differentiation of the oxidation states of iron is achieved by using mathematical equations to overcome the interference of Fe(III) in the spectrophotometric determination of Fe(II) when they are both present in the same solution. In this manner the time-consuming and labor-intensive steps of preoxidation of Fe(II) or reduction of Fe(III) are eliminated. By preconcentrating a 10-mL sample solution detection limits as low as 7 microg L(-1), were obtained after a single-step extraction procedure. The relative standard deviation (n=4, 30 microg L(-1)) was 2.6 % and 1.8 % for spectrophotometry and FAAS, respectively. Recoveries in the range of 96-105 % were obtained by analysis of spiked real samples. The method was further verified by analyzing a certified reference material (IMEP-9); for this the recovery was 98.5 %.     

Targeted Multiresidue Method for the Analysis of Different Classes of Pesticides in Agro-Food Industrial Sludge by Liquid Chromatography Tandem Mass Spectrometry

Sludge generated after washing of fruits and vegetables during agro-food processes is a complex matrix and selective methods for the identification and quantification of pesticides’ residues are necessary in order to achieve a sustainable and effective management of the total sewage. The present work describes the development and validation of a reliable, simple and fast analytical method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the determination of 47 pesticides of different chemical classes, including organosphosphates, pyrethroids, neonicotinoids, triazoles and others, in sludge samples after QuEChERS sample preparation. The necessity of the individual steps of QuEChERS was investigated and the LC-ESI-MS/MS conditions were optimized to achieve maximum sensitivity of the target analytes. The method limits of detection (LODs) ranged between 0.0005 mg/kg (imidacloprid) and 0.05 mg/kg (beta cyfluthrin). The recoveries ranged between 71–120% and the repeatability of the method was ≤25% expressed as relative standard deviation. The method was applied to sludge samples generated after washing of fruits in an agro-fruit-packaging unit in Greece. The results showed the presence of 37 pesticides’ active substances with concentrations ranging from low ppbs, such as fludioxinil (5 μg/kg) up to low ppms such as beta cyfluthrin (3.5 mg/kg) and with their sum concentration reaching up to 19 mg/kg.     

Baked-Potato Routing

This paper presents scheduling of packet transmission schemes, calledbaked-potatoschemes, which are used to avoid simultaneous arrival of packets at a switch. We present scheduling schemes for any capacity of links and switches. The schemes are evaluated by the maximal length of time between two successive schedulings of a processor. For the case of a single-capacity link and switch, our scheme is proved optimal by presenting a matching lower bound. Our baked-potato scheme does not assume any prior knowledge on the source–destination demands and can be used for sending control packets and broadcasting.     

On the incremental singular value decomposition method to support unsteady adjoint-based optimization

This paper proposes and evaluates an approximation model based on an incremental Singular Value Decomposition (iSVD) algorithm, for unsteady flow field reconstructions, needed for integrating the unsteady adjoint equations backward in time, within a gradient-based optimization loop. Due to the iSVD algorithm, the computational cost of solving the unsteady adjoint equations is reduced considerably, without practically affecting the accuracy of the computed gradient. Approximations to the unsteady flow fields are constructed while solving the time-varying flow equations (moving forward in time) and used to reconstruct these fields during the backward-in-time integration of the continuous adjoint equations. Optimization results obtained using the proposed method are compared to those computed using the binomial checkpointing technique, which acts as the reference method. Test cases for both flow control and shape optimization problems are presented.     

Thermal efficiency enhancement of nanofluid-based parabolic trough collectors

Journal of Thermal Analysis and Calorimetry - The use of nanofluids in parabolic trough collectors is one of the most promising techniques for enhancing their performance. The objective of this...     

A new framework for population balance modeling of spray fluidized bed agglomeration

Previous work(Hussain et al.(2013).Chemical Engineering Science,101,35) has pointed out that the conventional,one-dimensional population balance equation for aggregation can be expanded to accurately reproduce the results of discrete simulations of spray fluidized bed agglomeration.However,some parameters had to be imported from the discrete simulation(Monte-Carlo).The present paper shows how the expanded population balance can be run without importing parameters from the Monte-Carlo simulation.The expanded population balance still reproduces the results of Monte-Carlo simulations accurately,taking into account key micro-scale phenomena(sessile droplet drying,efficiency of collisions),but with much lower computational cost.Required input parameters are just the drying time of sessile droplets(calculated in advance),and the pre-factor of an equation that correlates particle collision frequency with fluidized bed expansion.In this way,the expanded population balance is,apart from autonomous,also(nearly) predictive.Its performance is demonstrated by comparisons with both Monte-Carlo results and experimental data for various operating conditions(binder mass flow rate,gas temperature).Despite formally being a one-dimensional expression,the expanded population balance captures additional properties,such as the number of wet particles and the number of droplets in the system,which are even difficult to measure in experiments.     

Sampling and refinement protocols for template-based macrocycle docking: 2018 D3R Grand Challenge 4

We describe a new template-based method for docking flexible ligands such as macrocycles to proteins. It combines Monte-Carlo energy minimization on the manifold, a fast manifold search method, with BRIKARD for complex flexible ligand searching, and with the MELD accelerator of Replica-Exchange Molecular Dynamics simulations for atomistic degrees of freedom. Here we test the method in the Drug Design Data Resource blind Grand Challenge competition. This method was among the best performers in the competition, giving sub-angstrom prediction quality for the majority of the targets.     

Evaluating energy efficiency and economic effect of heat transfer in copper tube for small solar linear Fresnel reflector

Journal of Thermal Analysis and Calorimetry - An experimental and numerical investigation of a small linear Fresnel for water heating application has been carried out in Blida, Algeria. The...     

Transient and asymptotic dynamics of a prey–predator system with diffusion

In this paper, we study a prey–predator system associated with the classical Lotka–Volterra nonlinearity. We show that the dynamics of the system are controlled by the ODE part. First, we show that the solution becomes spatially homogeneous and is subject to the ODE part as t → ∞ . Next, we take the shadow system to approximate the original system as D → ∞ . The asymptotics of the shadow system are also controlled by those of the ODE. The transient dynamics of the original system approaches to the dynamics of its ODE part with the initial mean as D → ∞ . Although the asymptotic dynamics of the original system are also controlled by the ODE, the time periods of these ODE solutions may be different. Concerning this property, we have that any δ > 0 admits D₀ > 0 such that if , the time period of the ODE, satisfies , then the solution to the original system with D ≥ D₀ cannot approach the stationary state. Copyright © 2012 John Wiley & Sons, Ltd.